My cutoff is a windchill of -25, though yesterday we went outside with a windchill of -27 because it has been so cold that we hadn't gone outside for days (it is back to -33 today). We dress appropriately and stayed out for about 20 minutes. Nice to get some fresh air. My new 1 year old started crying after about 15 minutes, but he is going to have to get used to it! Lol.